The present invention relates to a method and apparatus for surface treating animal tissue. More particularly, the invention relates to the use of hot water submersion techniques for reducing bacterial populations on the surface of animal tissue.
There exists concern about pathogenic and enteric bacteria in animal meat, and, in particular, ground beef. As a consequence of processing animals into meat for human consumption, the surface of the animal carcass may become contaminated with bacteria from many sources including processing equipment, workers, and the environment. The predominant source for bacterial contamination is the animal itself. The hide, hooves, intestinal contents, and milk have the potential to harbor not only large numbers of bacteria but also pathogenic bacteria. Techniques have been utilized for reducing bacterial contamination of the animal carcass. For example, International Publication No. WO 96/13983 describes an apparatus for steam pasteurization of the surface of meat carcasses. Other techniques for reducing the contamination of the carcass surface involves trimming defined areas on the carcass, and washing the carcass with both hot and cold water. These techniques are described by Phebus et al., xe2x80x9cComparison of Steamed Pasteurization and Other Methods for Reduction of Pathogens on Surfaces of Freshly Slaughtered Beef,xe2x80x9d Journal of Food Protection, vol. 60, no. 5, 1997, pages 476-484. Techniques for treating buffalo meat cuts from shoulder and leg portion in hot water at 70xc2x0 C. and 80xc2x0 C. for 30 to 60 seconds is described by Sachindra et al., xe2x80x9cReduction in Microbial Load on Buffalo Meat By Hot Water Dip Treatment,xe2x80x9d Meat Science, vol. 48, no. 1/2, pages 149-157, 1998.
Bacterial populations have the opportunity to form on the exposed carcass surface. A large percentage of the trimmings which are processed for human consumption are obtained from this exposed carcass surface. It has been found that E. coli bacteria, and many pathogens, can reside on the surface of carcass beginning with the carcass processing. The pathogens can originate from fecal matter and other contaminants on the surface of the meat. Without adequately destroying these pathogens, the meat is processed, and shipped to the distributor, retailer, or consumer. It is then left for the consumer or preparer of the meat to address the problem that by then can be even worse. The bacteria may have further multiplied. Ground meats are very susceptible to bacteria growth because the surface pathogens can be distributed throughout the meat during processing.
A method for surface treating animal tissue is provided by the present invention. The method includes steps of: providing animal tissue having an average size of between about 0.5 inch and about 16 inches in length; introducing the animal tissue into a fluid bath provided at a temperature of between about 80xc2x0 C. and about 150xc2x0 C. for between about 25 seconds and about 50 seconds; and recovering the animal tissue from the water bath.
The animal tissue which can be processed by the method of the invention can include beef, poultry, swine, sheep, horse and wild game. The animal tissue can be introduced into the fluid bath immediately or shortly after the slaughter or fabrication operation, or after the animal tissue has been cooled or chilled. In the case of animal tissue introduced shortly after the slaughter or fabrication operation, it is expected that the animal tissue will have a temperature of between about 30xc2x0 C. and about 40xc2x0 C. In the case of animal tissue which has been cooled or chilled, it is expected that the animal tissue will have a temperature of between about 0xc2x0 C. and 10xc2x0 C.
The animal tissue is preferably advanced through the fluid bath in a first in and first out arrangement. It should be appreciated that a first in and first out arrangement reflects the situation where portions of animal tissue do not remain or build up within the hot fluid bath. That is, tissue enters the hot fluid bath and then is removed after the desired level of surface treatment. In order to provide a first in and first out arrangement, the animal tissue is preferably advanced or conveyed through the water bath using a rotation screw having a spiral flight extending from a first end to a second end for advancing the animal tissue. Preferably, the rotation screw rotates at a rate of about one revolution per minute and about 20 revolutions per minute.
While the preferred heating media or bath is water, it should be appreciated that other types of heating media can be used including tallow. When water is used as the heating medium, it is preferable to provide the hot water at a temperature of between about 80xc2x0 C. and 110xc2x0 C., and to provide a surface treating period of between about 25 seconds and about 50 seconds. In the case of using tallow as a heating media, it may be appropriate to increase the treatment time if the temperature of the heating media is maintained at between about 80xc2x0 C. and about 110xc2x0 C. Accordingly, at this temperature, it may be appropriate to surface treat the animal tissue for a period of between about 25 seconds and about 150 seconds. Alternatively, the tallow can be provided at a higher temperature to provide a shorter treatment period. For example, the tallow can be provided at a temperature of between about 115xc2x0 C. and 150xc2x0 C. in order to provide a treatment time which is between about 25 seconds and 50 seconds. In addition, the size of the animal tissue can be characterized in terms of weight. Preferably, the average weight of a piece of animal tissue is between about 0.25 lb. and about 12 lbs.
The invention relates to a method for preparing ground beef. The method includes the steps for surface treating animal tissue followed by a step of processing the recovered animal tissue to provide ground beef.
A pasteurization unit is provided by the present invention. The pasteurization unit includes a hot media containing trough, a rotation screw, and a motor for driving the rotation screw. The hot media containing trough has an animal tissue inlet at a first end, and an animal tissue outlet at a second end. The hot media containing trough is preferably constructed and arranged for holding hot media and animal tissue having an average size of between about 0.25 lb. and about 12 lbs. per piece of animal tissue, and for providing surface treating of the animal tissue. By xe2x80x9chot mediaxe2x80x9d it is meant that the temperature of the media is provided at a temperature which is sufficient to provide lethal action on the bacterial populations which may be present on the present of the animal tissue during the time of surface treating the animal tissue. In general, it is expected that the media will be provided at a temperature of between about 80xc2x0 C. and about 150xc2x0 C. under most desirable periods for surface treating the animal tissue. Preferably, the media includes water, and may include fat or tallow. The rotation screw is provided having a spiral flight extending from the first end to the second end. The spiral flight is provided for advancing the animal tissue from the first end to the second end. The motor is provided for driving the rotation screw at a speed of between about one and about 20 revolutions per minute. Preferably, the pasteurization unit includes hot media inlet ports along a length of the hot water containing trough or introducing hot media into the hot media containing trough.